KR101789270B1 - Coated Steel Sheet and Exterior Building Material - Google Patents

Abstract

The coated steel sheet has a steel sheet and an overcoating film disposed on the steel sheet, the undercoating film including a chromate-based anticorrosive pigment and an aggregate as primary particles, and not containing pore particles, and an overcoating film disposed on the undercoating film. The aggregate satisfies the following equations (1) and (2).
D _10? 0.6 T ... (1), D ₉₀ < 2.0 T ... (2)
Here, D ₁₀ is a 10% particle diameter (μm) of the aggregate in the cumulative particle size distribution on the number basis. D ₉₀ is the 90% particle size (μm) of the aggregate in the cumulative particle size distribution on the number basis. And T is a film thickness (μm) of a portion of the undercoating film where the aggregate does not exist.

Description

Coated Steel Sheet and Exterior Building Material [0001]

The present invention relates to a coated steel sheet excellent in corrosion resistance and damage resistance, and an exterior construction material including the coated steel sheet.

When a painted steel sheet is used as an exterior building material, the occurrence of red rust (red rust) becomes a problem. For example, red rust is generated in an exposed portion of a steel plate, such as an end surface of a coated steel sheet or a bending process, in an area where harm is not a problem (a non-corrosive area), and deterioration of the appearance due to this occurs. Such occurrence of red rust can be effectively prevented by applying a chromate-based chemical treatment to the steel sheet or by adding a chromic acid-based rust preventive pigment to the underlying coating film. However, even if such measures are taken, it is not possible to completely prevent the generation of red rust (red rust) over a long period of time, and therefore, there is a demand for a coated steel sheet capable of further preventing the generation of red rust in the exposed portion of the steel sheet.

If the coated steel sheet is used as exterior construction materials, the damage to the coated steel sheet may be required. As a technique for improving the scratch resistance of the coated steel sheet, it has been proposed to add silica particles having a particle diameter of 1 to 5 占 퐉 into the underlying coating film (see Patent Document 1). By increasing the surface roughness of the underlying coating by adding silica particles in the underlying coating, the contact area between the underlying coating and the overcoat increases, and the adhesion strength of the overcoating coating to the underlying coating increases. As a result, the damage resistance of the coated steel sheet is improved.

Patent Document 1: JP-A-9-122579

As means for improving both the corrosion resistance and the damage resistance of the coated steel sheet, it is conceivable to add silica particles capable of increasing the surface roughness of the chromium-base anticorrosive pigment and the undercoating film to the undercoating film with reference to Patent Document 1 . However, according to the preliminary experiment of the present inventors, it was found that the coated steel sheet obtained in this manner had excellent initial corrosion resistance (rust resistance) and scratch resistance, but the corrosion resistance (rust resistance) was rapidly lowered with the lapse of time .

An object of the present invention is to provide a coated steel sheet excellent in both corrosion resistance and scratch resistance and an exterior construction material including the coated steel sheet.

The inventors of the present invention have found that the above problems can be solved by adding a chromic acid-based rust preventive pigment and primary aggregate to an undercoating film, and further study has been completed to complete the present invention.

That is, the present invention relates to the following coated steel sheets and exterior construction materials.

[1] A steel plate comprising: a steel plate; a coating film disposed on the steel plate, the coating film comprising a chromic acid-based anticorrosive pigment and aggregate as primary particles and not containing pore particles; and an overcoating film disposed on the undercoat film, Satisfies the following expressions (1) and (2): " (1) "

D _10? 0.6 T ... (One)

D ₉₀ <2.0 T ... (2)

Here, D10 is a 10% particle size (mu m) of the aggregate in the cumulative particle size distribution based on the number. D90 is the 90% particle size ([mu] m) of the aggregate in the cumulative particle size distribution on the number basis. And T is a film thickness (μm) of a portion of the undercoating film where the aggregate does not exist.

[2] The coated steel sheet according to [1], wherein the ratio of the aggregate to the solid content of the undercoating film is 1% by volume or more and less than 10% by volume.

[3] The coated steel sheet according to [1] or [2], wherein the steel sheet is subjected to chemical conversion treatment.

[4] An exterior construction material including the coated steel sheet according to any one of [1] to [3].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a coated steel sheet and an exterior construction material excellent in both corrosion resistance and scratch resistance.

A coated steel sheet according to the present invention has a steel sheet (a coated original plate), an undercoated film formed on the steel plate, and a coated film formed on the underlying coated film. Hereinafter, each component of the coated steel sheet according to the present invention will be described.

(Original plate)

The kind of the steel sheet to be coated is not particularly limited. Examples of the coated plate include a cold-rolled steel plate, a galvanized steel plate, a Zn-Al alloy plated steel plate, a Zn-Al-Mg alloy plated steel plate, an aluminum coated steel plate, a stainless steel plate (austenitic, martensitic, ferritic, Site two-phase system). From the viewpoint of corrosion resistance, light weight, and cost effectiveness, it is preferable that the coated original plate is a molten 55% Al-Zn alloy plated steel sheet. The steel sheet may be subjected to a known coating pretreatment such as rubbing or pickling. The thickness of the steel sheet is not particularly limited and may be suitably set according to the use of the coated steel sheet. For example, the thickness of the steel sheet is about 0.1 to 2 mm.

The steel sheet (coated original plate) may be subjected to chemical conversion treatment from the viewpoint of improving the corrosion resistance and the coating film adhesion (scratch resistance) of the coated steel sheet. The kind of chemical conversion treatment is not particularly limited. Examples of the chemical treatment include a chromate treatment, a chrome-free treatment, a phosphate treatment and the like.

The conversion treatment can be carried out by a known method. For example, the chemical conversion treatment liquid may be applied to the surface of a steel sheet by a roll coating method, a spin coating method, a spraying method, or the like, and dried without washing with water. The drying temperature and the drying time are not particularly limited as long as moisture can be evaporated. From the viewpoint of productivity, the drying temperature is preferably in the range of 60 to 150 占 폚 at the reached substrate temperature, and the drying time is preferably in the range of 2 to 10 seconds. The deposition amount of the chemical conversion coating film is not particularly limited as long as it is effective for improving the corrosion resistance and the film adhesion. For example, in the case of a chromate film, the deposition amount may be adjusted so that the total Cr-equivalent adhesion amount is 5 to 100 mg / m ² . The chrome-free coating one case, Ti-Mo composite film in the 10 ~ 500 mg / m ^2, acid-containing film with the fluorine conversion coating weight or the total metal elements in terms of adhesion amount is 3 ~ 100 mg / m ² range coating weight so that I of the fluoroalkyl . In the case of the phosphate coating, the adhesion amount may be adjusted to 5 to 500 mg / m ² .

(Undercoat)

The underlying coating is formed on the surface of the steel sheet or chemical conversion coating. The undercoating film contains anticorrosive pigments and aggregates and improves the corrosion resistance of the coated steel sheet and the coating film adhesion (scratch resistance).

The type of the resin (base resin) constituting the undercoating film is not particularly limited. Examples of the resin constituting the undercoating film include epoxy resin, acrylic resin, polyester and the like.

From the viewpoint of improving the corrosion resistance, the undercoating film is blended with a hexavalent chromic acid-based anticorrosive pigment. The kind of the chromic acid-based anticorrosive pigment is not particularly limited. Examples of chromic acid-based anticorrosive pigments include strontium chromate, zinc chromate, calcium chromate, manganese chromate, and magnesium chromate. The total amount of the chromic acid-based anticorrosive pigment is not particularly limited, but is preferably in the range of 1 to 50% by volume, more preferably in the range of 5 to 20% by volume based on the solid content of the underlying coating film. If the total amount is less than 1% by volume, corrosion resistance may not be effectively improved. When the total amount is more than 50% by volume, the coatability, workability and / or film adhesion may be impaired.

From the viewpoint of improving the damage resistance, the undercoating film is mixed with an aggregate. By increasing the surface roughness of the underlying coating by adding aggregate in the underlying coating, the contact area between the underlying coating and the overcoat increases, thereby improving the adhesion strength of the overcoating coating to the underlying coating. Thus, the damage resistance of the coated steel sheet can be improved.

The chromic acid-based anticorrosive pigment exhibits an effect of imparting corrosion resistance by eluting from the underlying coating film. On the other hand, if the pore particles (pore particles) are mixed as an aggregate in the undercoating film, the anticorrosive pigment becomes more liable to elute through the gaps in the aggregate, and the corrosion resistance may be lost in a short period of time. Therefore, in the coated steel sheet according to the present invention, primary particles are mixed as an aggregate. Here, the term "pore particle" means a particle including pores that can be a passage of a rust-preventive pigment, and includes the aggregate of fine particles or particles of a porous structure. The term &quot; primary particles &quot; means particles not containing pores that can be a passage of a rust preventive pigment. On the other hand, the primary particles may have a concave portion that does not become a passage of the anticorrosive pigment. For example, the aggregate may be a primary particle (resin particle) made of a resin such as an acrylic resin, a polyurethane, a polyester, a melamine resin, a urea resin, or a polyamide; (Inorganic particles) composed of inorganic compounds such as glass, silicon carbide, boron nitride, zirconia, alumina, and silica. The shape of the primary particles is preferably substantially spherical, but may be other shapes such as a columnar shape or a disk shape.

The particle size of the aggregate is not particularly limited, but preferably satisfies the following equations (1) and (2). In the following equations (1) and (2), D ₁₀ is the 10% particle size (μm) of the aggregate in the cumulative particle size distribution on the number basis. D ₉₀ is the 90% particle size (μm) of the aggregate in the cumulative particle size distribution on the number basis. T is the film thickness (μm) of the portion where the aggregate does not exist in the underlying coating. If the following expression (1) is not satisfied, there is a possibility that the surface roughness of the underlying coating film becomes small and the damage resistance can not be effectively improved. If the following expression (2) is not satisfied, the aggregate may easily separate from the underlying coating film, and the damage resistance may be lowered.

D _10? 0.6 T ... (One)

D ₉₀ <2.0 T ... (2)

On the other hand, the particle diameters of the above-mentioned formulas (1) and (2) are measured by, for example, the Coulter counter method. However, even if the particle diameters measured by other measurement methods, , It is possible to effectively improve the damage resistance. For example, the particle size of an aggregate in an undercoating film can be measured by the following procedure. First, the coated steel sheet is cut and the cut surface is polished. Then, the cross section is observed with an electron microscope to obtain the cross section of the undercoating film. Then, the long side length and the short side length are measured for all the aggregates existing in the field of view on the cross section, and the individual average particle sizes are calculated. Then, the particle size is the particle count number starting with small, it calculates a particle size of 10% of the entire number of the particles, where D _10, the diameter of the 90% where as D _90.

The amount of the aggregate to be incorporated is not particularly limited, but is preferably in the range of 1% by volume or more and less than 10% by volume based on the solid content of the underlying coating film. When the total amount is less than 1% by volume, there is a fear that the damage resistance can not be effectively improved. In addition, since the amount of aggregate which is a barrier against the elution of the chromic acid-based anticorrosive pigment is small, the chromic acid-based anticorrosive pigment may be excessively eluted and the corrosion resistance may be lost in a short period of time. When the total amount is 10 vol% or more, the elution of the chromic acid-based anticorrosive pigment is excessively inhibited, which may lower the corrosion resistance.

The film thickness of the underlying coating film is not particularly limited, but is preferably in the range of 1 to 10 탆. When the film thickness is less than 1 탆, there is a possibility that the corrosion resistance can not be sufficiently improved. On the other hand, when the film thickness is more than 10 mu m, blistering easily occurs during drying of the paint, which may deteriorate the appearance of the coated steel sheet (such as occurrence of blisters during drying of the paint). Even if the film thickness of the undercoating film is made more than 10 mu m, the effect on cost is small.

The undercoat may be formed by a known method. For example, an undercoating material including a base resin, a chromic acid-based anticorrosive pigment and an aggregate may be applied to the surface of a coated plate (steel plate) and then heat-treated at an ultimate substrate temperature of 150 to 280 ° C for 10 to 60 seconds. On the other hand, when the heat treatment temperature is less than 150 ° C, the paint can not be heat-treated sufficiently, and there is a possibility that the function of the undercoating film can not be sufficiently exhibited. On the other hand, when the heat treatment temperature is higher than 280 占 폚, the adhesion between the undercoat film and the overcoat film may be deteriorated due to excessive heat treatment. The method of applying the undercoating material is not particularly limited and may be suitably selected from the methods used for the production of the precoated steel sheet. Examples of such a coating method include a roll coating method, a flow coating method, a curtain flow method, a spray method and the like.

(Coating film)

The overcoating film is formed on the underlying coating. Coating films improve the design and corrosion resistance of painted steel sheets.

The type of the resin (base resin) constituting the coating film to be applied is not particularly limited. Examples of the resin constituting the coating film to be overlaid include polyester, epoxy resin, acrylic resin and the like. Such a resin may be crosslinked by a curing agent. The kind of the curing agent may be appropriately selected depending on the kind of resin used, the printing conditions, and the like. Examples of the curing agent include a melamine compound, an isocyanate compound, and the like. Examples of the melamine compound include melamine compounds of imino group, methylolimino group, methylol group or fully alkyl group type.

The coating film to be coated may be transparent or may be colored by blending any coloring pigment. Examples of the coloring pigment include inorganic pigments such as titanium oxide, calcium carbonate, carbon black, iron oxide, titanium yellow, red iron oxide, cobalt blue, cerium blue, ultramarine, cobalt green and molybdate orange; A composite oxide calcined pigment including a metal component such as CoAl, CoCrAl, CoCrZnMgAl, CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi, MnSbTi, FeCr, FeCrNi, FeNi, FeCrNiMn, CoCr, Mn, Co and SnZnTi; Al, resin-coated metallic pigments such as Al and Ni; And first yellow G, first yellow G, first yellow G, first yellow G, first red G, first yellow G, first yellow G, first yellow G, first yellow G, first yellow G, first yellow G, , Organic pigments such as Watching Red, Benzidine Yellow, Benzidine Orange, Bonmaron L, Bonmaron M, Brilliant First Scarlet, Vermilion Red, Phthalocyanine Blue, Phthalocyanine Green, First Sky Blue, and Aniline Black. The overcoating film may contain other pigments such as extender pigments. Examples of extender pigments include barium sulfate, titanium oxide, silica, calcium carbonate and the like.

The film thickness of the overcoat film is not particularly limited, but is preferably in the range of 5 to 30 占 퐉. When the film thickness is less than 5 탆, there is a possibility that a desired appearance can not be given. On the other hand, when the film thickness is more than 30 占 퐉, blisters tend to be formed at the time of drying the paint, which may deteriorate the appearance of the painted steel sheet (such as occurrence of water film at the time of drying the paint).

The coating film to be coated may be formed by a known method. For example, an overlay paint including a base resin, a coloring pigment, and an extender pigment may be applied to the surface of a coated original plate (steel plate) and heat-treated at an ultimate substrate temperature of 150 to 280 ° C for 20 to 80 seconds. On the other hand, when the heat treatment temperature is less than 150 ° C, the paint can not be heat-treated sufficiently, and there is a possibility that the function of the coated film can not be sufficiently exhibited. On the other hand, when the flame temperature is higher than 280 DEG C, there is a possibility that the properties such as molding process, weather resistance, and corrosion resistance may not be sufficiently exhibited due to oxidation deterioration of the resin due to excessive heat treatment. The method of applying the coating material for overcoating is not particularly limited and may be appropriately selected from the method used for producing the precoated steel sheet. Examples of such a coating method include a roll coating method, a flow coating method, a curtain flow method, a spray method and the like.

(Back coating)

The coated steel sheet according to the present invention may have a coating film (back coating film) on the surface opposite to the surface on which the underlying coating film and the over coating film are formed. The back coating may be a single coating or two coatings. The kind of the resin constituting the back coating film and the kind of the pigment are not particularly limited either. For example, a known coating can be applied by a known method to form a back coating.

(effect)

Since the coated steel sheet according to the present invention includes the anticorrosive pigment which is easy to elute in the undercoating film, the generation of red rust can be prevented in the steel plate exposed portion such as the end face of the coated steel sheet and the bending process. Further, since the coated steel sheet according to the present invention contains an aggregate composed of primary particles in the undercoating film, it is excellent in the damage resistance while preventing the excessive dissolution of the anticorrosive pigment. That is, the coated steel sheet according to the present invention is excellent in short-term and long-term corrosion resistance and scratch resistance. Therefore, the coated steel sheet according to the present invention is very suitable as an exterior building material of a building, which is used, for example, in a portion which is exposed to the outside air and can be irradiated with sunlight.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

<Examples>

1. Manufacture of painted steel sheet

A 55% Al-Zn plated steel sheet (SPCC, coated on both sides: 150 g / m ² ) was prepared as a coating base plate. After the surface of the coated plate was subjected to alkali degreasing, chemical treatment was carried out using a coating type chromate treatment liquid (Surfcot NRC300NS; manufactured by Nippon Paint Co., Ltd.).

The undercoat paint was coated on the surface of the chemically treated coated original plate with a roll coater and dried at an ultimate substrate temperature of 200 占 폚 for 30 seconds to form a base coat having a thickness of 2 to 8 占 퐉. As the undercoat paint, 5% by volume of barium sulfate as an extender pigment was added to a commercially available epoxy-based clear paint (NSC680; Nippon Paint Coatings Co., Ltd.), and the rust-preventive pigment and / Prepared. The particle diameters (D ₁₀ and D ₉₀ ) of the aggregate are the particle diameters in the cumulative particle size distribution based on the number measured by the Coulter counter method and are adjusted using a sieve.

Then, a coating material to be applied to the surface of the undercoating film was applied by a roll coater and dried at an ultimate substrate temperature of 220 DEG C for 45 seconds to form an overcoat film having a thickness of 10 mu m. As an overcoat paint, a commercially available polyester clear paint (CA; manufactured by Nippon Pine Coatings Co., Ltd.) containing 7% by volume of carbon black as a color pigment was prepared.

Table 1 shows the composition of the undercoating film of the coated steel sheet thus produced. In the category of aggregates in Table 1, A1 is acrylic resin particles (primary particles) (Atopearl J-4P; Negami Kyo Co., Ltd.). A2 is an acrylic resin particle (primary particle) (Turfic FH-S010; Toyobo Co., Ltd.). A3 is acrylic resin particles (primary particles) (Turfic FH-S005; Toyobo Co., Ltd.). A4 is an acrylic resin particle (primary particle) (Turfic FH-S008; Toyobo Co., Ltd.). A5 is an acrylic resin particle (primary particle) (Atopearl J-5P; Negami Kyo Co., Ltd.). B is a urethane resin particle (primary particle) (Ato Pearl P-800 T; Negami Kyo Co., Ltd.). C is glass particles (primary particles) (EMB-10; Pottas-baroltini Co., Ltd.). D is hard silica particles (fine pore particles) (Sarisia 430; manufactured by Fuji Silysia Chemical Co., Ltd.). In the column of the kind of the anticorrosive pigment in Table 1, a is strontium chromate. b is zinc chromate. and c is chromium (III) oxide. d is chromium (III) sulfate. In Table 1, the blending amount of the aggregate and the anticorrosive pigment is a ratio (volume%) to the solid content of the undercoating film. In Table 1, the film thickness is the thickness of the portion where the aggregate does not exist in the underlying coating.

2. Evaluation test

(1) Corrosion resistance test

A plate was cut from each coated steel sheet by shearing, and 2T bending was carried out to prepare a test piece. The test piece has a cutting end surface and a bending process, and the steel original plate and the plating metal are exposed at the portion.

Each test specimen was placed in the outdoors (non-salted area) of Kiyu Ryu City, Gunma Prefecture and subjected to a 6-month and 2-year atmospheric exposure test. Each specimen was installed at an inclination angle of 35 ^{° to} the south. The bend was placed on the underside of the specimen. After 6 months and two years from the start of exposure, area ratios of the red rust occurrence portions in the steel end plate exposed portions of the cutting end face and the bending portion were measured. , &Quot;?&Quot;,&quot;?&Quot;,&quot;?&Quot;,&quot; did. Quot ;, &quot;?&Quot;, or &quot;?&Quot;, it can be said that the coated steel sheet has the necessary corrosion resistance.

(2) The damage test

The damage resistance test was carried out by using a Clemens type scratch hardness tester on the assumption that the coated steel sheet was damaged at the time of handling and construction. A coin made of stainless steel was placed on the evaluation plate so that the surface of the horizontally disposed evaluation plate was inclined at 45 ^° . The coating film of the plate for evaluation was scraped hard with a coin while a predetermined load was applied to the coin, and the minimum load when the plating layer was observed was recorded as an evaluation value. The evaluation was evaluated as &quot;?&Quot; when the evaluation value was 2000 g or more, &quot;?&Quot; when the evaluation value was less than 2000 g and less than 2000 g, and &quot;Quot;,&quot;&amp; cir &amp;&quot;, it can be said that the coated steel sheet has necessary damage resistance.

(3) Evaluation results

The evaluation results of the corrosion resistance test and the damage resistance test of each coated steel sheet are shown in Table 2.

As shown in Table 2, the coated steel sheets No. 23 and No. 24, to which no aggregate is added to the underlying coating, are inferior in damage resistance. Further, in the case where the aggregate of pore particles is added to the undercoating film, The coated steel sheets 18 and 19 have excellent damage resistance, but are inferior in long-term corrosion resistance. This is considered to be because the aggregate is pore particles, and the chromic acid-based anticorrosive pigment has eluted to the outside in a short period of time via a gap (pore) in the aggregate. The coated steel sheets No. 9 to No. 17 in which D ₁₀ or D ₉₀ of the aggregate do not satisfy the above-mentioned formula (1) or (2) are inferior in damage resistance. The fact that the damage resistance of the coated steel sheets No. 9, 10, 12, 13, 15, and 16 was poor was due to the fact that the small aggregate did not contribute to the increase of the contact area between the underlying coating and the overcoated coating do. It is considered that the damage resistance of the coated steel sheets No. 9, 11, 12, 14, 15 and 17 is inferior due to the fact that large aggregates are easily separated from the underlying coating film with respect to the film thickness of the underlying coating film.

The coated steel sheets No. 20 to 23 containing trivalent chromium as the anticorrosive pigment in the undercoating film and the coated steel sheets No. 25 and 26, in which the anticorrosive pigment is not added to the underlying coating film, are inferior in short-term and long-term corrosion resistance.

On the other hand, the coated steel sheets No. 1 to 8, in which chromate-based anticorrosive pigments and aggregates composed of primary particles of a predetermined size were added to the undercoating film, were excellent in short-term and long-term corrosion resistance and scratch resistance.

From the above results, it can be seen that the coated steel sheet according to the present invention is excellent in both corrosion resistance and scratch resistance.

The present application claims priority based on Japanese Patent Application No. 2014-159568 filed on August 5, 2014. The contents of the application specification and drawings are all incorporated herein by reference.

&Lt; Industrial Availability >

The coated steel sheet according to the present invention is excellent in both corrosion resistance and scratch resistance, and is thus useful, for example, for exterior building materials of buildings.

Claims (4)

Steel plate,
An undercoat film comprising a chromate based anticorrosive pigment disposed on the steel sheet and an aggregate composed of primary particles not containing pores,
And an overcoating film disposed on the underlying coating film,
The aggregate satisfies the following equations (1) and (2)
Painted steel plate.
D _10? 0.6 T ... (One)
D ₉₀ <2.0 T ... (2)
Here, D ₁₀ is a 10% particle diameter (μm) of the aggregate in the cumulative particle size distribution on the number basis. D ₉₀ is the 90% particle size (μm) of the aggregate in the cumulative particle size distribution on the number basis. And T is a film thickness (μm) of a portion of the undercoating film where the aggregate does not exist. The method according to claim 1,
Wherein the ratio of the aggregate to the solid content of the undercoat is at least 1 volume% and less than 10 volume%. The method according to claim 1,
Wherein the steel sheet is subjected to chemical conversion treatment. An exterior construction material comprising the coated steel sheet according to any one of claims 1 to 3.